Fish and shellfish can be an important part of healthy diet. They are a good source of high-quality protein and nutrients and are low in saturated fat. A well-balanced diet that includes a variety of fish and shellfish can contribute to a child’s proper growth and development. In addition, the American Heart Association recommends that adults eat fish at least twice a week for a healthier heart.

Many fish, including the most popular store-bought fish and shellfish, are safe to eat. Some, however, contain chemicals (such as methylmercury, polychlorinated biphenyls (PCBs), and various types of pesticides) that may harm children and adults. The Maryland Department of the Environment monitors and evaluates contamination levels in fish, shellfish, and crabs throughout Maryland and issues guidelines for recreationally caught fish (see our most recent guidelines). The U.S. Food and Drug Administration (FDA) issues nationwide guidance for commercial fish (fish bought in stores and restaurants). In March 2004, the FDA together with the Environmental Protection Agency (EPA) released the following national guidelines for women who may become pregnant, pregnant women, nursing mothers, and young children:

DO NOT EAT Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.

Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury.

Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.

Another commonly eaten fish, albacore ("white") tuna has more mercury than light canned tuna. So, when choosing your two meals of fish and shellfish, you may eat up to 6 ounces (one average meal) of albacore tuna per week.

Check local guidelines about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don't consume any other fish during that week.

The Maryland Department of the Environment (MDE) is responsible for monitoring and evaluating contaminant levels in fish, shellfish and crabs in Maryland waters. The tissues of interest for human health include the edible portions of fish (fillet), crab (crabmeat and "mustard"), and shellfish ("meats"). Such monitoring enables MDE to determine whether the specific contaminant levels in these species are within safe limits for human consumption. Results of such studies are used to issue consumption guidelines for recreationally caught fish, shellfish, and crab species in Maryland (see our most recent guidelines). Additionally, since fish, shellfish, and crabs have the potential to accumulate inorganic and organic chemicals in their tissues (even when these materials are not detected in water), monitoring of these species becomes a valuable indicator of environmental pollution in a given waterbody.

Fish Tissue Monitoring

The Maryland Department of the Environment has monitored chemical contaminant levels in Maryland’s fish since the early 1970s. The current sampling design divides the State into five regions:

Eastern Shore waterbodies,

Harbors and Bay,

Metro waterbodies,

Western Bay tributaries, and

Western Maryland waterbodies.

Maryland routinely monitors core sampling sites within these five regions on a 5-year cycle. When routine monitoring indicates potential hazards to the public and environment, additional monitoring of the affected area may be conducted to verify the initial findings and identify the appropriate species and size classes associated with harmful contaminant levels. Findings from such studies are the basis for the fish consumption guidelines (see our most recent guidelines).

The types of fish sampled include important predatory game species (such as small mouth bass and striped bass), common recreational panfish species (white perch, bluegill, crappie) as well as, bottom dwelling, accumulator species with relatively high fat content (such as carp, catfish and American eel). Also, periodically MDE conducts intensive surveys of contaminant levels in selected species in specific water bodies. Past targets of intensive surveys conducted in Patapsco River/Baltimore Harbor included: white perch, channel catfish, eel, and striped bass.

Shellfish Monitoring

Since the 1960's, the Maryland Department of the Environment has been surveying metal and pesticide levels in oysters and clams from the Chesapeake Bay and its tributaries. Prior to 1990, this effort was conducted every one or two years. In response to low levels of contaminants found and very little change from year to year, shellfish are not monitored routinely for chemical contaminants. This allows MDE to devote its limited resources towards intensive surveys if needed in areas where contamination is more likely.

While monitoring has shown no chemical contaminants at levels of concern in any of the oysters sampled, recreational harvesters should still be aware of possible bacterial contamination and avoid shell-fishing in areas that are closed to commercial shellfish harvesting.

Between 2001-2003 blue crabs were sampled in the following locations throughout Maryland:

Chesapeake Bay:

- off Hart-Miller Island- mouth of Fairlee Creek- near Sandy Point- off Tilghman Point- off Fairhaven- between Cedar & Cove Points- off Point No Point

Gunpowder River

Patapsco River/Baltimore Harbor

Potomac River

Crabmeat and hepatopancreas (also known as “mustard” or green gland) were analyzed separately. While crabmeat was low in contaminants, the “mustard” contained elevated levels of PCBs and other contaminants in the following locations:

Cedar Point,

Fairlee Creek,

Hart-Miller Island,

Middle River, and

Patapsco River/Baltimore Harbor.

Specific recommendations for crab “mustard” have not been developed for all locations, however in general, it is advised that the crab “mustard” from crabs taken from the Northern Chesapeake Bay (above Magothy River) should be consumed in moderation, while “mustard” from the above locations should be eaten sparingly and avoided for the crabs from the Patapsco River/Baltimore Harbor.